Educate me on valves/springs

[digger]

I recall the same, and I also recall there was another change made

the one i saw from PC had exhaust mods and it was fairly clear that those changes were influencing making it impossible to draw much in the way of conclusions. So i still maintain no one has posted a comparison of cams and cams alone on these forums with same engine so a lot of peoples beliefs may very well be unfounded.
Yet whenever i've seen gains from stock cams to 280/272 or stock to 288/280 the respective deltas on different setups don't support the 280/272 having all the top end without the bottom end losses that the 288 have.

[C///M]

I recall the same, and I also recall there was another change made

I don't remember the specifics, but sometime before the CatCams groupbuy closed, there was some info about the additional gains with the longer durations. That's what prompted me to decide on them.

Also a couple weeks ago, Paul told me he had made even more progress on his 288/80 tunes after a lot more experience so I had him update my cams bin.

Regardless, I don't think you can go wrong and I think the choice is best left to personal preference and intended usage.

[jbfrancis3]

I could have sworn made a post shortly before the plug was pulled that he wouldn’t take those at face value or something along those lines.

I recall the same, and I also recall there was another change made

[terra]

Yeah, I’m running 280/272.

you'll have to ask him to confirm, but I’m pretty sure Paul was one of the first people to do same car, same Dyno, optimized tune for each, 280/272 vs 288/280, and show that 280/272 made more power in the mid/low range and same same peak power.

I could have sworn made a post shortly before the plug was pulled that he wouldn’t take those at face value or something along those lines.

[Obioban]

I read that over the years reg: 288/80 vs 280/72 until more recent data from Paul and Hassan regarding gains with the 288/80. I have tunes from Paul so we'll see where I end up, but this car does spend most of it's time up in the rev range. I have a couple base tunes for the cams from him until I setup a Dyno session.

Yeah, I’m running 280/272.

you'll have to ask him to confirm, but I’m pretty sure Paul was one of the first people to do same car, same Dyno, optimized tune for each, 280/272 vs 288/280, and show that 280/272 made more power in the mid/low range and same same peak power.

[digger]

Yeah I’ve not seen same engine the two cam setups compared.

[C///M]

I believe he runs 280/272. Over the years on m3forum, it became settled science that 280/272s are actually better everywhere than 288/280 given normal rev ranges. Not sure exactly how fast you'd want to spin the thing to take advantage of the 288s, but I'd love to see some dynos differentiating the 2 duration options reposted here on nam3forum.

I read that over the years reg: 288/80 vs 280/72 until more recent data from Paul and Hassan regarding gains with the 288/80. I have tunes from Paul so we'll see where I end up, but this car does spend most of it's time up in the rev range. I have a couple base tunes for the cams from him until I setup a Dyno session.

[ethan]

Last question: are you running 88/80 or 80/72? Did you bump your revs past 8200 at all? You guys are talking me out of it. The more I think about it, the more I think I'll wait to pull the head and then do valves and springs at that time instead. Considering this season is getting shortened, I'll do my best to be smart/conservative and just throw the cams in and leave everything else alone for now; see how the car is first.

I believe he runs 280/272. Over the years on m3forum, it became settled science that 280/272s are actually better everywhere than 288/280 given normal rev ranges. Not sure exactly how fast you'd want to spin the thing to take advantage of the 288s, but I'd love to see some dynos differentiating the 2 duration options reposted here on nam3forum.

[digger]

I can appreciate your sentiment, but this car has everything else. After this, the only other changes will be vincebar and CF roof panel.

My goal is to retire this car from track duty in the next couple years and build a w2w car.

Btw I was talking about CSL valves.

It’s ok replace valve springs but normally you check the spring loads at installed height and over the nose and compare to new and see how much they relaxed before changing them. Valve springs are one of the most highly stressed components

[C///M]

When I installed my cams, my car had ~140,000 miles on it, including ~15,000 track miles, and I did not. Doesn't really matter how cheap they are if replacing them has no benefit, and any time you fiddling with engine internals you risk not reassembly correctly and having engine failure.

If I was doing anything, it would be new valve guide/seals, but they also seem to last a LONG time... so holding off on that till it's actually necessary. Plus, cam install is only a 4-5 hour project-- not in so deep that I felt compelled to replace anything/everything.

Last question: are you running 88/80 or 80/72? Did you bump your revs past 8200 at all? You guys are talking me out of it. The more I think about it, the more I think I'll wait to pull the head and then do valves and springs at that time instead. Considering this season is getting shortened, I'll do my best to be smart/conservative and just throw the cams in and leave everything else alone for now; see how the car is first.

[Obioban]

Here's my question, for a car that sees a lot of track, where my home track has a couple sections I'd like to raise to say 8500, and you're installing cams and rockers, would you go ahead with new springs while you're at it? They're pretty cheap.

That said, associated little parts costs also go up.

When I installed my cams, my car had ~140,000 miles on it, including ~15,000 track miles, and I did not. Doesn't really matter how cheap they are if replacing them has no benefit, and any time you fiddling with engine internals you risk not reassembly correctly and having engine failure.

If I was doing anything, it would be new valve guide/seals, but they also seem to last a LONG time... so holding off on that till it's actually necessary. Plus, cam install is only a 4-5 hour project-- not in so deep that I felt compelled to replace anything/everything.

[C///M]

Yeah, I haven't heard of the stock valve springs wearing out on any time line... if you're not trying to rev it over ~8700rpm, I don't think you're going to get any benefit to replacing them.

Here's my question, for a car that sees a lot of track, where my home track has a couple sections I'd like to raise to say 8500, and you're installing cams and rockers, would you go ahead with new springs while you're at it? They're pretty cheap.

That said, associated little parts costs also go up.

[Obioban]

Yeah, I haven't heard of the stock valve springs wearing out on any time line... if you're not trying to rev it over ~8700rpm, I don't think you're going to get any benefit to replacing them.

[terra]

I can appreciate your sentiment, but this car has everything else. After this, the only other changes will be vincebar and CF roof panel.

My goal is to retire this car from track duty in the next couple years and build a w2w car.

Replacing the springs would truly be a waste of money IMO. There will be zero benefit, even long term.

CSL exhaust valves... probably not truly worth the money, but if you’re trying to squeeze out every last drop of volumetric efficiency, then I can see the argument.

[C///M]

Sounds like a waste of money. Spend money on stuff that’s going to make a tangible difference

I can appreciate your sentiment, but this car has everything else. After this, the only other changes will be vincebar and CF roof panel.

My goal is to retire this car from track duty in the next couple years and build a w2w car.